The invention relates to a method for producing precursors for 2-[18F]fluorophenylalanine (2-[18F]FPhe) and 6-[18F]fluoro-L-meta-tyrosine (6-[18F]FMT) and the α-methylated derivatives thereof, to the precursor, and to a method for producing 2-[18F]fluorophenylalanine and 6-[18F]fluoro-L-meta-tyrosine and the α-methylated derivatives thereof from the particular precursor.
A publication from the year 2001 by T. Tierling, K. Hamacher, and H. H. Coenen entitled “A new nucleophilic asymmetric synthesis of 6-[18F]Fluoro-DOPA”, is known, which was published in J. Label. Compds. Radiopharm. 44, Suppl. 1 and which describes a method for producing an [18F]FDOPA precursor and the conversion thereof into 6-[18F]fluoro-DOPA. According to this method, a precursor is converted into [18F]FDOPA using a K2CO3 cryptand complex by nucleophilic substitution. The product obtained has an enantiomeric purity of 85%.
An electrophilic synthesis of 6-[18]− and 4-[18F]fluoro-L-meta-tyrosine is known from the article “Synthesis of 6-[18]− and 4-[18F]Fluoro-L-meta-tyrosines via Regioselective Radiofluorodestannylaton” by the authors M. Namavari et. al. in Appl. Radiat. Isot. Vol 44, No. 3, pp 527-536 from 1993.
The methods for producing 2-[18F]FPhe and 2-[18F]FMT precursors known from the prior art result in relatively low radiochemical yields and are therefore associated with high cost.